Wattle function and territoriality in the South Island saddleback (Philesturnus carunculatus)1
Thesis DisciplineBiological Sciences
Degree GrantorUniversity of Canterbury
Degree NameBachelor of Science (Hons)
The South Island saddleback (Philesturnus carunculatus) is an endangered bird endemic to New Zealand. Both males and females possess wattles, which are colourful fleshy structures that hang from the lower beak. Although a wide range of birds have wattles, the selection pressures and behavioural function of these biological ornaments remain poorly understood. In this study, behavioural observations, morphological measures, and a playback experiment were used to investigate how wattles are used by South Island saddlebacks in their natural habitat. Wattles were found to be monomorphic when body mass was accounted for, and they were observed to engorge in both aggressive and non-aggressive visual displays. In the playback experiment, wattle engorgement in saddlebacks was significantly associated with territorial intrusions in males but not in females, although females were significantly more likely to engorge their wattles and display in the absence of their mate. Larger males with bigger wattles did not have significantly stronger territorial responses. These results provide the first experimental evidence for the functional role that wattle engorgement plays in saddleback signalling behaviour. The markedly similar visual display behaviour between sexes, which is used in both aggressive and non-aggressive contexts, provides insight into possible selection pressures acting in the evolutionary maintenance of wattles.
SubjectsField of Research::06 - Biological Sciences::0603 - Evolutionary Biology
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